Phospholipids are a major component of the photoreceptor membranes and the cell membranes of the neural retina. They comprise a wide variety of classes, each of which is a heterogeneous group of molecular species due to the presence of acyl chains of various lengths and various numbers of double bonds. One outstanding feature of retinal phospholipids is the high content of docosahexaenoate. It is not known if docosahexaenoate is acylated during phosphatidic acid synthesis or if it is acylated in the preformed lipids by acylation-deacylation cycles in the retina. This pilot project aims to define precisely which step is involved. This information will provide the basis for further long-term studies on the regulation of the formation of the phospholipids in retinal membranes, i.e., photoreceptors, in the normal retina as well as in retinas with degenerative disease. We intend to test the rat eye for use as an in vivo experimental model in the study of the synthesis of phosphatidic acid in the retina. Wistar rats of 200-300g body weight will be lightly anesthetized and injected intravitreally with 5 microliters of a solution of one of the following amphiphilic cationic drugs: propranolol, fenfluoramine, chloroquine, propranolol glycol, or sodium fluoride. To enable us to follow the biosynthesis of phosphatidic acid, an intravitreal injection of (2- 3H)glycerol will be given within minutes after the drug injection. The rats will be decapitated at intervals after injection, the eyes will be enucleated, and the retinas excised. Molecular species will be separated by chromatography. Lipids will be digested with perchloric acid, and phosphorus will be colorimetrically quantified. Proteins will be assessed by the procedure of Lowry et al. Radioactivity will be determined by liquid scintillation counting with the use of Triton-X-100-water-Omnifluor. In addition, intravitreal injections of (1- 1 4C)docosahexaenoate will be given to determine if this molecule is acylated prior to phosphatidic acid synthesis.